Here's why:

* It doesn't produce its own light. Jupiter is a gas giant, meaning it's primarily composed of gases like hydrogen and helium. Unlike stars, it doesn't undergo nuclear fusion to create light.

* It reflects sunlight. The light we see from Jupiter is actually sunlight that is reflected off its clouds. Those clouds are composed of various gases and materials, which scatter and reflect the sunlight.

* It's quite reflective. Jupiter is known for its bright appearance in the night sky, and this is because it reflects a lot of the sunlight that falls on it.

So, while Jupiter may appear to be shining, it's really just acting as a giant mirror, reflecting the sun's light back to us.